Study on proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) of water in muscle and liver of mice at different ages will be continued to complement the data already obtained. The study is at 30 MHz and 25 degrees C. Na ion, K ion and water content of the tissues will be determined and correlated with the relaxation data. Proton T1 of water on hydrated collagen will be carried out using collagen crosslinked with formaldehyde and modified by dansyl chloride or 1-fluoro-2,4-dinitrobenzene. The dependence on spin-locking field strength of proton T1 rho (spin-lattice relaxation time in the rotating framework) at different water contents in muscle will be investigated. Off-resonance T1 rho study of 2H and 17 O for muscle water will be made. Diffusion coefficient of water in muscle and collagen and Na ions in muscle will be measured by spin echo technique.